IKAROS and AIOLOS directly regulate AP-1 transcriptional complexes and are essential for NK cell development.

Ikaros transcription factors are essential for adaptive lymphocyte function, yet their role in innate lymphopoiesis is unknown. Using conditional genetic inactivation, we show that Ikzf1/Ikaros is essential for normal natural killer (NK) cell lymphopoiesis and IKZF1 directly represses Cish, a negative regulator of interleukin-15 receptor resulting in impaired interleukin-15 receptor signaling. Both Bcl2l11 and BIM levels, and intrinsic apoptosis were increased in Ikzf1-null NK cells, which in part accounts for NK lymphopenia as both were restored to normal levels when Ikzf1 and Bcl2l11 were co-deleted. Ikzf1-null NK cells presented extensive transcriptional alterations with reduced AP-1 transcriptional complex expression and increased expression of Ikzf2/Helios and Ikzf3/Aiolos. IKZF1 and IKZF3 directly bound AP-1 family members and deletion of both Ikzf1 and Ikzf3 in NK cells resulted in further reductions in Jun/Fos expression and complete loss of peripheral NK cells. Collectively, we show that Ikaros family members are important regulators of apoptosis, cytokine responsiveness and AP-1 transcriptional activity.

DOT1L maintains NK cell phenotype and function for optimal tumor control.

Histone methyltransferases (HMTs) are crucial in gene regulation and function, yet their role in natural killer (NK) cell biology within the tumor microenvironment (TME) remains largely unknown. We demonstrate that the HMT DOT1L limits NK cell conversion to CD49a+ CD49b+ intILC1, a subset that can be observed in the TME in response to stimulation with transforming growth factor (TGF)-ß and is correlated with impaired tumor control. Deleting Dot1l in NKp46-expressing cells reveals its pivotal role in maintaining NK cell phenotype and function. Loss of DOT1L skews NK cells toward intILC1s even in the absence of TGF-ß. Transcriptionally, DOT1L-null NK cells closely resemble intILC1s and ILC1s, correlating with altered NK cell responses and impaired solid tumor control. These findings deepen our understanding of NK cell biology and could inform approaches to prevent NK cell conversion to intILC1s in adoptive NK cell therapies for cancer.